The hydrogen peroxide oxidation of 2,2,6,6-tetramethylpiperidines with hydrogen peroxide alone, or with carbonate catalyst, of with divalent metal catalyst is known. U.S. Pat. Nos. 5,654,434 and 5,777,126 describe the oxidation using hydrogen peroxide alone. U.S. Pat. No. 5,629,426 discloses the use of carbonate catalyzed hydrogen peroxide oxidations. U.S. Pat. No. 5,416,215 describes the use of divalent metal catalysts for the hydrogen peroxide oxidation reaction.
E. G. Rozantsev et al., Synthesis, 1971, 190 disclose the use of tungstate catalyst for the hydrogen peroxide oxidation of 2,2,6,6-tetramethylpiperidines.
U.S. Pat. No. 5,204,473 describes the use of tert-butyl hydroperoxide for the oxidation of 2,2,6,6-tetramethylpiperidines to the corresponding N-oxyl compounds. I. Q. Li et al., Macromolecules 1996, 29, 8554 and T. J. Connolly et al., Tetrahedron Letters, 1996, 37, 4919 describe the use of di-tert-butyl peroxide for the same purpose.
G. G. Barclay et al., Macromolecules, 1997, (30), 1929 describe the formation of a diadduct of a nitroxyl with an activated double bond (styrene).
L. J. Johnson et al., J. of Organic Chem., 1986, (51), 2806 describe the photochemical hydrogen atom abstraction by nitroxyls followed by N--OR formation.
T. J. Connolly et al., Tetrahedron Letters, 1997, (38), 1133 disclose the thermal abstraction of benzylic hydrogen atoms followed by N--OR formation.
I. A. Opeida et al., Kinetics and Catalysts, 1995, (36), 441 (translation from Russian) also describe the thermal abstraction of benzylic hydrogen atoms.
The instant process differs significantly from each of these prior art references and provides the use of environmentally friendly hydrogen peroxide with water as an oxidation by-product. The formation of 4-functionalized N--OR derivatives is obtained without the use of organic peroxides and hydroperoxides.